This invention relates to a tenter frame and method especially useful for treating textile webs wherein a single pair of longitudinally aligned bearings carry each tenter clip on an opposite side of a monorail and wherein guidance is provided by low friction material on the tenter clip, at the top of the monorail and under a chain carrying the tenter clips.
Monorails have been used primarily for tenter frames in the manufacture of plastic film such as illustrated in U.S. Pat. No. 3,457,608 wherein longitudinally aligned bearings are provided at the top of the monorail and additional bearings are provided for supporting the tenter clips on rails, with all monorail guidance accomplished by rolling element bearings. Such constructions are expensive in that mounting the required number of rolling element bearings in several vertical and horizontal planes creates a large, complex and heavy tenter chain and track system. It is desirable to use monorail constructions of laminated bands or strips so as to facilitate limited angular displacement of adjacent track sections when necessary. This is made possible because the laminated flexible metal bands or strips are easily configured for passing about curves such as those encountered in tenter frames and the like, and can be constructed in lengths which allow them to be mounted to the entire length of the tenter as one piece.
The tenter frame illustrated herein is especially useful in processing of textile material but such frames are also useful in other webs such as plastic film utilized in photographic film and the like. The use of plastic wear strips is illustrated in U.S. Pat. Nos. 4,926,529 and 5,068,214 which are constructed of suitable polyamide materials such as Vespel. This anti-friction material may be advantageously used in bearings and in wear strips or wear pads for supporting the tenter clips and chains during operation. A tenter chain of this type is illustrated in U.S. Pat. No. 4,260,844.
It is desirable to provide tentering apparatus of inexpensive construction which may be used particularly in textiles wherein substantial loads may be supported by longitudinally spaced pairs of aligned bearings which receive symmetrical, in line loads imposed by the web which lies in the same plane. Inexpensive wear strips and the like constructed of suitable anti-friction material, such as polyamide, may be utilized as guides for the ball bearing members and the tenter clips. Anti-friction guides may be configured in such a way that the loads on wear strips are minimal. Thus, wear strips and pads serve in large measure for guidance only rather than as force resisting members without causing undue friction. It has been found that such construction may be effectively used because of its simplicity, compact size, light weight and because of the advantageous use of wear strips in combination with the longitudinally spaced, aligned ball bearing members.
The state of the art is further illustrated in the following U.S. Pat. Nos. 3,055,048, 3,142,108, 3,240,412, 3,457,608, 3,469,291, 3,500,515, 3,580,451, 3,638,289, 4,080,692, 4,134,189, 4,176,429, 4,435,884, 4,639,984, 4,736,498, 4,815,181, 4,882,820, 4,890,365, 5,161,674, 5,265,313, 5,341,547, and 5,390,398.